This is the Team Associated 46 Tooth RC8T3.1 Differential Ring Gear. This ASC81014 46T ring gear is standard on the T3.1 and T3.1e, both of which come with V3 differentials.

V3 diffs offer increased fluid capacity, more consistency over a run, and the ability to use HTC (High Torque Capacity) or LTC (Low Torque Capacity) internal gear sets. With this ring gear, racers using the previous generation T3 and T3e trucks may now upgrade to V3 differentials to take advantage of its benefits.